In conventional cement based paints portland cement is the principal constituent, serving as a binder, and generally comprises over 60%, by weight, of the composition. The cement is blended with lime, up to 25% by weight of the composition, along with an accelerator such as calcium chloride, mineral fillers and coloring agents to form a dry powder. When mixed with water in a 1:1 ratio by volume the mixture forms a slurry which is applied in two or more coats over a primed surface. White cement plus dolomite mixed with water to form a slurry is applied as a primer coat to fill in open pores, cracks and the like of the plastered surface in order to reduce the consumption of the more expensive cement paint in obtaining a complete, smooth, finished layer. Due to the relatively high content of portland cement and relatevely low surface area dependent upon the particle size of the mix, coloring agents/pigments tend to bleed or migrate under weathering effects over a period of time deleteriously affecting the homogeneity of the finish. Since conventional cement paint powders are generally coarse in texture they do not adhere well to smooth plastered surfaces and consequently require an application of liquid cement primer to obtain proper adhesion or bonding on smooth surfaces.
It is an object of the present invention to provide a coating material for masonry type surfaces which does not have the limitations of the prior art as noted above. Another object of the invention is the provision of an improved coating material for use on exterior or interior surfaces of a variety of materials including masonry, concrete, bricks, cement blocks, asbestos cement sheets, gypsum boards and the like which has a homogenous finish. Yet another object is the provision of coating material which has improved covering or hiding properties so that a single application over a primed surface will result in a suitable finish. Still another object is the provision of a coating material with improved dispersion of coloring agents and with minimized or essentially no bleeding or migration.
Conventional mosaic and terrazzo tiles of various dimensions up to 24".times.24"are made by blending portland cement, dolomite/calcite powder and mosaic chips in various colors and sizes, eg, 1 to 5 mm in diameter with a typical mix proportion being 1:1.5:2. The required amount of water at a ratio of water to cement of approximately 0.45 is added and the thick slurry is then pressed at about 150 to 200 kg/square cm in hydraulic presses in thicknesses of about 8 to 10 mm as a topper over a base of grey cement-sand mix in thicknesses of about 14 to 16 mm. The pressed tiles are cured with water and steam and finally polished to obtain an even topper surface amd to expose mosaic chips giving a terrazzo type finish.
It is an object of another embodiment of the invention to provide a finishing material system wherein the conventional topper layer can be applied in situ at the site of use and without the need of using high pressures. Yet another object is the provision of an improved finished or topper layer for either compartmented or seemless finishes which is less expensive to produce and yet has increased strength and hardness to make it more durable.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of the invention.